Power amplifier module

ABSTRACT

A power amplifier module includes an amplifier transistor and a bias circuit. A first power supply voltage based on a first operation mode or a second power supply voltage based on a second operation mode is supplied to the amplifier transistor. The amplifier transistor receives a first signal and outputs a second signal obtained by amplifying the first signal. The bias circuit supplies a bias current to the amplifier transistor. The bias circuit includes first and second resistors and first and second transistors. The first transistor is connected in series with the first resistor and is turned ON by a first bias control voltage which is supplied when the first operation mode is used. The second transistor is connected in series with the second resistor and is turned ON by a second bias control voltage which is supplied when the second operation mode is used.

BACKGROUND

The present disclosure relates to a power amplifier module.

In mobile communication devices, such as cellular phones, a poweramplifier module for amplifying power of a signal to be transmitted to abase station is used. Nowadays, in cellular phones, modulation methodsusing standards for high-speed data communication, such as HSUPA(High-Speed Uplink Packet Access), LTE (Long Term Evolution), andLTE-Advanced, are being used. In these communication standards, forenhancing the communication speed, it is desirable to decrease a phasedeviation and an amplitude deviation. Accordingly, it is necessary thata power amplifier module implement high linearity. In theabove-described communication standards, for achieving the enhancedcommunication speed, the range in which the amplitude of a signalchanges (dynamic range) is usually wide. For maintaining high linearityeven in the case of a wide dynamic range, a high power supply voltage isnecessary, and this is likely to increase the power consumption in apower amplifier module.

On the other hand, in cellular phones, for increasing the maximum talktime or the maximum communication time, it is desirable to decrease thepower consumption. For example, Japanese Unexamined Patent ApplicationPublication (Translation of PCT Application) No. 2005-513943 discloses apower amplifier module utilizing the envelope tracking technique. In theenvelope tracking technique, by adjusting the power supply voltage inaccordance with the amplitude level of an input modulation signal, thepower efficiency is improved.

BRIEF SUMMARY

Envelope tracking is effective particularly for enhancing power-addedefficiency when a power amplifier is operating under high power. On theother hand, when a power amplifier is operating under low power, anothertechnique, such as average power tracking, is sometimes used forimproving the linearity of the gain.

Generally, a power amplifier module includes a bias circuit forsupplying bias to a power amplifier transistor. The bias circuitincludes a transistor at its base to which a bias control voltage issupplied and a ballast resistor connected to the emitter of thetransistor. A suitable value of the bias control voltage and a suitableresistance value of the ballast resistor of a power amplifier modulevary in accordance with the operation mode and the output level of thepower amplifier module. It is thus difficult to provide the optimal biascircuit adjusted to all operation modes.

The present disclosure has been made in view of such a background.Accordingly, the present disclosure suitably controls bias to besupplied to an amplifier transistor in a power amplifier module that isoperable in multiple operation modes.

According to embodiments of the present disclosure, there is provided apower amplifier module including an amplifier transistor and a biascircuit. A first power supply voltage based on a first operation mode ora second power supply voltage based on a second operation mode issupplied to the amplifier transistor. The amplifier transistor receivesa first signal and outputs a second signal obtained by amplifying thefirst signal. The bias circuit supplies a bias current to the amplifiertransistor. The bias circuit includes first and second resistors andfirst and second transistors. The first transistor is connected inseries with the first resistor and is turned ON by a first bias controlvoltage which is supplied when the first operation mode is used. Thesecond transistor is connected in series with the second resistor and isturned ON by a second bias control voltage which is supplied when thesecond operation mode is used.

According to embodiments of the present disclosure, it is possible tosuitably control bias to be supplied to an amplifier transistor in apower amplifier module that is operable in multiple operation modes.

Other features, elements, characteristics and advantages of the presentdisclosure will become more apparent from the following detaileddescription of embodiments of the present disclosure with reference tothe attached drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an example of the configuration of a transmittingunit including a power amplifier module, which is an embodiment of thepresent disclosure;

FIG. 2 illustrates an example of the configuration of a power amplifiermodule;

FIG. 3 illustrates an example of the configuration of bias circuits;

FIG. 4A is a graph illustrating an example of the relationship betweenthe output level (dBm) and the power-added efficiency (%) when a poweramplifier module is operating in the envelope tracking (ET) mode;

FIG. 4B is a graph illustrating an example of the relationship betweenthe output level (dBm) and the gain (dB) when a power amplifier moduleis operating in the average power tracking (APT) mode;

FIG. 5 illustrates an example of the configuration of a bias circuitwhen an amplifier transistor is a multi-finger transistor;

FIG. 6 illustrates another example of the configuration of the biascircuit when the amplifier transistor is a multi-finger transistor;

FIG. 7 illustrates an example of the configuration of the bias circuit;

FIG. 8 illustrates another example of the configuration of the biascircuit;

FIG. 9 illustrates another example of the configuration of the biascircuit when the amplifier transistor is a multi-finger transistor;

FIG. 10 illustrates another example of the configuration of the biascircuit when the amplifier transistor is a multi-finger transistor;

FIG. 11 illustrates another example of the configuration of the biascircuit;

FIG. 12 illustrates another example of the configuration of the biascircuit;

FIG. 13 illustrates another example of the configuration of the biascircuit when the amplifier transistor is a multi-finger transistor;

FIG. 14 illustrates another example of the configuration of the biascircuit; and

FIG. 15 illustrates another example of the configuration of the biascircuit.

DETAILED DESCRIPTION

An embodiment of the present disclosure will be described below withreference to the accompanying drawings. FIG. 1 illustrates an example ofthe configuration of a transmitting unit 100 that includes a poweramplifier module 113, which is an embodiment of the present disclosure.The transmitting unit 100 is used for transmitting various signals, suchas audio and data signals, to a base station, in a mobile communicationdevice, such as a cellular phone. The transmitting unit 100 supportsmultiple radio frequency (RF) bands (multiband). The mobilecommunication device also includes a receiving unit for receivingsignals from a base station. However, an explanation of the receivingunit will be omitted.

As shown in FIG. 1, the transmitting unit 100 includes a basebandsection 110, an RF section 111, a power supply circuit 112, a poweramplifier module 113, a front-end section 114, and an antenna 115.

The baseband section 110 modulates an input signal, such as an audiosignal or a data signal, on the basis of a modulation method, such asHSUPA or LTE, and outputs a modulation signal. In this embodiment, amodulation signal output from the baseband section 110 is an IQ signal(I (In-phase) signal and Q (Quadrature) signal) representing theamplitude and the phase on an IQ plane. The frequency of an IQ signalis, for example, about several MHz to several tens of MHz.

The baseband section 110 also outputs a mode signal MODE which specifiesan operation mode of the power amplifier module 113. In this embodiment,the power amplifier module 113 is operable in the envelope tracking (ET)mode and the average power tracking (APT) mode. If the output of thepower amplifier module 113 is a predetermined level or higher, thebaseband section 110 outputs a mode signal MODE which specifies the ETmode. If the output of the power amplifier module 113 is lower than thepredetermined level, the baseband section 110 outputs a mode signal MODEwhich specifies the APT mode.

The baseband section 110 also outputs a control signal for controllingthe power supply voltage in accordance with the operation mode of thepower amplifier module 113. More specifically, in the case of the ETmode, the baseband section 110 detects the amplitude level of amodulation signal on the basis of the IQ signal, and outputs a powersupply control signal CTRL_(ET) to the power supply circuit 112 so thata power supply voltage V_(REG) to be supplied to the power amplifiermodule 113 will be at a level corresponding to the amplitude level of anRF signal. On the other hand, in the case of the APT mode, the basebandsection 110 outputs a power supply control signal CTRL_(APT) to thepower supply circuit 112 so that a power supply voltage V_(REG) to besupplied to the power amplifier module 113 will be at a levelcorresponding to the average power of the power amplifier module 113.

The RF section 111 generates an RF signal (RF_(IN)) used for performingradio transmission from the IQ signal output from the baseband section110. The frequency of the RF signal is about several hundreds of MHz toseveral GHz. In this case, instead of performing direct conversion fromthe IQ signal into the RF signal, the RF section 111 may first convertthe IQ signal into an IF (Intermediate Frequency) signal and thenconvert the IF signal into the RF signal.

The power supply circuit 112 generates a power supply voltage V_(REG) ata level corresponding to the operation mode, on the basis of the modesignal MODE and the power supply control signal CTRL_(ET) or CTRL_(APT),and supplies the generated power supply voltage V_(REG) to the poweramplifier module 113. More specifically, in the case of the ET mode, thepower supply circuit 112 generates a power supply voltage V_(REG) (firstpower supply voltage) corresponding to the power supply control signalCTRL_(ET). In the case of the APT mode, the power supply circuit 112generates a power supply voltage V_(REG) (second power supply voltage)corresponding to the power supply control signal CTRL_(APT). The powersupply circuit 112 may include a DC-to-DC converter which generates apower supply voltage V_(REG) at a desired level from an input voltage(for example, a battery voltage V_(BAT)).

The power amplifier module 113 amplifies power of the RF signal(RF_(IN)) output from the RF section 111 to a level which is high enoughto be transmitted to a base station, on the basis of the power supplyvoltage V_(REG) supplied from the power supply circuit 112, and outputsan amplified signal (RF_(OUT)).

The front-end section 114 performs filtering on the amplified signal(RF_(OUT)) and switching between the amplified signal (RF_(OUT)) and asignal received from a base station. The amplified signal output fromthe front-end section 114 is transmitted to the base station via theantenna 115.

FIG. 2 illustrates an example of the configuration of the poweramplifier module 113. As shown in FIG. 2, the power amplifier module 113includes transistors 200 _(A) and 200 _(B), bias circuits 210 _(A) and210 _(B), matching circuits 220, 221, and 222, inductors 230 _(A) and230 _(B), and a bias control circuit 240.

The transistors 200 _(A) and 200 _(B) form a two-stage amplifier, whichamplifies an input RF signal (RF_(IN)) and outputs an amplified signal(RF_(OUT)). The transistors 200 _(A) and 200 _(B) are each constitutedby a bipolar transistor, for example, a heterojunction bipolartransistor (HBT). The first-stage (driving-stage) transistor 200 _(A)amplifies the input RF signal (RF_(IN)) and outputs the amplifiedsignal. The second-stage transistor 200 _(B) amplifies the signal outputfrom the transistor 200 _(A) and outputs the amplified signal. Thenumber of stages of the amplifier is not restricted to two, and may beone or three or more.

The bias circuits 210 _(A) and 210 _(B) supply bias to the transistors200 _(A) and 200 _(B), respectively. The bias circuit 210 _(A) suppliesa bias current I_(BIAS1) corresponding to a bias control signal S_(C1)output from the bias control circuit 240 to the transistor 200 _(A). Thebias circuit 210 _(B) supplies a bias current I_(BIAS2) corresponding toa bias control signal S_(C2) output from the bias control circuit 240 tothe transistor 200 _(B).

The matching circuits 220, 221, and 222 are disposed for performingimpedance matching between circuits. The matching circuits 220, 221, and222 are each constituted by, for example, inductors and capacitors.

The inductors 230 _(A) and 230 _(B) are disposed for the isolation ofthe RF signal. The power supply voltage V_(REG) is supplied to thetransistors 200 _(A) and 200 _(B) via the inductors 230 _(A) and 230_(B), respectively. In the power amplifier module 113 shown in FIG. 2,the power supply voltage V_(REG) is supplied to both of the transistors200 _(A) and 200 _(B). However, the power supply voltage V_(REG) may besupplied to only one of the transistors 200 _(A) and 200 _(B), and apower supply voltage of a predetermined level, for example, the batteryvoltage V_(BAT), may be supplied to the other one of the transistors 200_(A) and 200 _(B).

The bias control circuit 240 outputs the bias control signals S_(C1) andS_(C2) to the transistors 200 _(A) and 200 _(B), respectively, on thebasis of the mode signal MODE so that bias to be supplied to thetransistors 200 _(A) and 200 _(B) will be at a suitable levelcorresponding to the operation mode (ET/APT mode). The control operationusing the bias control signals S_(C1) and S_(C2) will be discussedlater. The bias control circuit 240 may be disposed outside of the poweramplifier module 113.

FIG. 3 illustrates an example of the configuration of the bias circuits210 _(A) and 210 _(B). A bias circuit 210 _(A1) includes transistors 300_(A) _(_) ₁ and 300 _(A) _(_) ₂ (first and second transistors) andresistors 310 _(A) _(_) ₁, 310 _(A) _(_) ₂, 312 _(A) _(_) ₁ (firstresistor), and 312 _(A) _(_) ₂ (second resistor). As shown in FIG. 3,the bias control signal S_(C1) output from the bias control circuit 240includes bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂ (firstand second bias control voltages), and the bias control signal S_(C2)output from the bias control circuit 240 includes bias control voltagesV_(C2) _(_) ₁ and V_(C2) _(_) ₂.

The transistors 300 _(A) _(_) ₁ and 300 _(A) _(_) ₂ are bipolartransistors, for example, HBTs. The bias control voltage V_(C1) _(_) ₁is supplied to the base of the transistor 300 _(A) _(_) ₁ via theresistor 310 _(A) _(_) ₁. The bias control voltage V_(C1) _(_) ₂ issupplied to the base of the transistor 300 _(A) _(_) ₂ via the resistor310 _(A) _(_) ₂. A power supply voltage of a predetermined level, forexample the battery voltage V_(BAT), is supplied to the collectors ofthe transistors 300 _(A) _(_) ₁ and 300 _(A) _(_) ₂.

One end of the resistor 312 _(A) _(_) ₁ is connected to the emitter ofthe transistor 300 _(A) _(_) ₁ and the other end thereof is connected tothe base of the transistor 200 _(A). That is, the resistor 312 _(A) _(_)₁ is connected in series with the transistor 300 _(A) _(_) ₁. One end ofthe resistor 312 _(A) _(_) ₂ is connected to the emitter of thetransistor 300 _(A) _(_) ₂ and the other end thereof is connected to thebase of the transistor 200 _(A). That is, the resistor 312 _(A) _(_) ₂is connected in series with the transistor 300 _(A) _(_) ₂. Theresistance value R_(B1) _(_) ₁ of the resistor 312 _(A) _(_) ₁ isdifferent from the resistance value R_(B1) _(_) ₂ of the resistor 312_(A) _(_) ₂.

In the bias circuit 210 _(A1), one of the transistors 300 _(A) _(_) ₁and 300 _(A) _(_) ₂ is turned ON under the control of the bias controlvoltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂. Then, the bias currentI_(BIAS1) is output via one of the transistors 300 _(A) _(_) ₁ and 300_(A) _(_) ₂ that is turned ON and the resistor 312 _(A) _(_) ₁ or 312_(A) _(_) ₂ connected in series with this transistor. This controloperation will be described below more specifically. For example, whenthe bias control voltage V_(C1) _(_) ₁ is at a high level and the biascontrol voltage V_(C1) _(_) ₂ is at a low level, the transistor 300 _(A)_(_) ₁ is turned ON and the transistor 300 _(A) _(_) ₂ is turned OFF. Inthis case, the bias circuit 210 _(A1) outputs the bias current I_(BIAS1)determined by the bias control voltage V_(C1) _(_) ₁ and the resistancevalue R_(B1) _(_) ₁. When the bias control voltage V_(C1) _(_) ₁ is at alow level and the bias control voltage V_(C1) _(_) ₂ is at a high level,the transistor 300 _(A) _(_) ₁ is turned OFF and the transistor 300 _(A)_(_) ₂ is turned ON. In this case, the bias circuit 210 _(A1) outputsthe bias current I_(BIAS1) determined by the bias control voltage V_(C1)_(_) ₂ and the resistance value R_(B1) _(_) ₂.

The configuration of the bias circuit 210 _(B1) is similar to that ofthe bias circuit 210 _(A1). Elements of the bias circuit 210 _(B1)equivalent to those of the bias circuit 210 _(A1) are designated by likereference numerals, and an explanation thereof will be omitted. In thebias circuit 210 _(B1), as well as in the bias circuit 210 _(A1), theresistance value R_(B2) _(_) ₁ of the resistor 312 _(B) _(_) ₁ isdifferent from the resistance value R_(B2) _(_) ₂ of the resistor 312_(B) _(_) ₂.

In the bias circuit 210 _(B1), for example, when the bias controlvoltage V_(C2) _(_) ₁ is at a high level and the bias control voltageV_(C2) _(_) ₂ is at a low level, the transistor 300 _(B) _(_) ₁ isturned ON and the transistor 300 _(B) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(B1) outputs the bias current I_(BIAS2)determined by the bias control voltage V_(C2) _(_) ₁ and the resistancevalue R_(B2) _(_) ₁. When the bias control voltage V_(C2) _(_) ₁ is at alow level and the bias control voltage V_(C2) _(_) ₂ is at a high level,the transistor 300 _(B) _(_) ₁ is turned OFF and the transistor 300 _(B)_(_) ₂ is turned ON. In this case, the bias circuit 210 _(B1) outputsthe bias current I_(BIAS2) determined by the bias control voltage V_(C2)_(_) ₂ and the resistance value R_(B2) _(_) ₂.

In the power amplifier module 113, in the case of the ET mode, the biascontrol voltages V_(C1) _(_) ₁ and V_(C2) _(_) ₁ are made to have a highlevel, while the bias control voltages V_(C1) _(_) ₂ and V_(C2) _(_) ₂are made to have a low level. In contrast, in the case of the APT mode,the bias control voltages V_(C1) _(_) ₁ and V_(C2) _(_) ₁ are made tohave a low level, while the bias control voltages V_(C1) _(_) ₂ andV_(C2) _(_) ₂ are made to have a high level. With this controloperation, the power amplifier module 113 is able to generate a biascurrent based on a suitable bias control voltage and a suitableresistance value corresponding to the operation mode. The value of thebias control voltage V_(C1) _(_) ₁ at a high level may be different fromthat of the bias control voltage V_(C1) _(_) ₂. For example, the biascontrol voltage V_(C1) _(_) ₁ at a high level (for example, about 2.85V) may be higher than the bias control voltage V_(C1) _(_) ₂ at a highlevel (for example, about 2.8 V). The relationship between the biascontrol voltages V_(C2) _(_) ₁ and V_(C2) _(_) ₂ may be similar to thatbetween the bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂.

FIG. 4A is a graph illustrating an example of the relationship betweenthe output level (dBm) and the power-added efficiency (%) when the poweramplifier module 113 is operating in the ET mode. FIG. 4A shows a changein the power-added efficiency in accordance with the magnitudes of thebias control voltage V_(C) (such as V_(C1) _(_) ₁ and V_(C1) _(_) ₂) andthe resistance value R_(B) (such as R_(B1) _(_) ₁ and R_(B1) _(_) ₂). Inthe ET mode, it is desirable to enhance the power-added efficiency. Itis thus necessary to determine the bias control voltage V_(C) and theresistance value R_(B) so as to increase the power-added efficiency.

FIG. 4B is a graph illustrating an example of the relationship betweenthe output level (dBm) and the gain (dB) when the power amplifier module113 is operating in the APT mode. FIG. 4B shows a change in the gain inaccordance with the magnitudes of the bias control voltage V_(C) (suchas V_(C1) _(_) ₁ and V_(C1) _(_) ₂) and the resistance value R_(B) (suchas R_(B1) _(_) ₁ and R_(B1) _(_) ₂). In the APT mode, it is desirable toenhance the linearity. It is thus necessary to determine the biascontrol voltage V_(C) and the resistance value R_(B) so as to obtainhigh linearity.

As shown in FIGS. 4A and 4B, the reference to be used for determiningthe bias control voltage V_(C) and the resistance value R_(B) in thecase of the ET mode is different from that in the case of the APT mode.Accordingly, the bias control voltage V_(C) and the resistance valueR_(B) suitable for one of the ET mode and the APT mode are notnecessarily the same as the bias control voltage V_(C) and theresistance value R_(B) suitable for the other mode. In terms of thispoint, in the power amplifier module 113, in each of the bias circuits210 _(A1) and 210 _(B1), the suitable bias control voltage V_(C) (forexample, V_(C1) _(_) ₁ or V_(C1) _(_) ₂) and the suitable resistancevalue R_(B) (for example, R_(B1) _(_) ₁ or R_(B1) _(_) ₂) can beselected in accordance with the operation mode. In this manner, in apower amplifier module which is operable in multiple operation modes, itis possible to control bias to be supplied to an amplifier transistor.

FIG. 5 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A2)) when the amplifier transistor 200 _(A) is amulti-finger transistor. Elements equivalent to those of the biascircuit 210 _(A1) are designated by like reference numerals, and anexplanation thereof will be omitted. When the amplifier transistor 200_(B) is a multi-finger transistor, the bias circuit 210 _(B) may beconfigured similarly to the bias circuit 210 _(A).

In the example shown in FIG. 5, the transistor 200 _(A) is constitutedby N unit transistors (fingers) 200 _(A) _(_) ₁ through 200 _(A) _(_)_(N) connected in parallel with each other. The bias circuit 210 _(A2)includes the same number of pairs of transistors 300 _(A) _(_) ₁ and 300_(A) _(_) ₂ (that is, transistors 300 _(A) _(_) ₁ _(_) ₁ through 300_(A) _(_) ₁ _(_) _(N) and transistors 300 _(A) _(_) ₂ _(_) ₁ through 300_(A) _(_) ₂ _(_) _(N), respectively) and the same number of pairs ofresistors 312 _(A) _(_) ₁ and 312 _(A) _(_) ₂ (that is, resistors 312_(A) _(_) ₁ _(_) ₁ through 312 _(A) _(_) ₁ _(_) _(N) and resistors 312_(A) _(_) ₂ _(_) ₁ through 312 _(A) _(_) ₂ _(_) _(N), respectively),which are provided in the bias circuit 210 _(A1), as the number (N) offingers.

In the bias circuit 210 _(A2), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistors 300 _(A) _(_) ₁ _(_) ₁through 300 _(A) _(_) ₁ _(_) _(N) are turned ON and the transistors 300_(A) _(_) ₂ _(_) ₁ through 300 _(A) _(_) ₂ _(_) _(N) are turned OFF. Inthis case, the bias circuit 210 _(A2) outputs the bias current I_(BIAS1)_(_) _(k) determined by the bias control voltage V_(C1) _(_) ₁ and theresistance value R_(B1) _(_) ₁ _(_) _(k) to the transistor 200 _(A) _(_)_(k) (k=1 to N). When the bias control voltage V_(C1) _(_) ₁ is at a lowlevel and the bias control voltage V_(C1) _(_) ₂ is at a high level, thetransistors 300 _(A) _(_) ₁ _(_) ₁ through 300 _(A) _(_) ₁ _(_) _(N) areturned OFF and the transistors 300 _(A) _(_) ₂ _(_) ₁ through 300 _(A)_(_) ₂ _(_) _(N) are turned ON. In this case, the bias circuit 210 _(A2)outputs the bias current I_(BIAS1) _(_) _(k) determined by the biascontrol voltage V_(C1) _(_) ₂ and the resistance value R_(B1) _(_) ₂_(_) _(k) to the transistor 200 _(A) _(_) _(k) (k=1 to N). With thisconfiguration, it is possible to obtain advantages similar to thoseachieved by the bias circuit 210 _(A1).

FIG. 6 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A3)) when the amplifier transistor 200 _(A) is amulti-finger transistor. Elements equivalent to those of the biascircuits 210 _(A1) and 210 _(A2) are designated by like referencenumerals, and an explanation thereof will be omitted. When the amplifiertransistor 200 _(B) is a multi-finger transistor, the bias circuit 210_(B) may be configured similarly to the bias circuit 210 _(A).

The bias circuit 210 _(A3) shown in FIG. 6 includes the same number ofresistors 312 _(A) _(_) ₁ (that is, 312 _(A) _(_) ₁ _(_) ₁ through 312_(A) _(_) ₁ _(_) _(N)), which are provided in the bias circuit 210_(A1), as the number (N) of fingers.

In the bias circuit 210 _(A3), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 300 _(A) _(_) ₁ isturned ON and the transistor 300 _(A) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(A3) outputs the bias current I_(BIAS1) _(_)_(k) determined by the bias control voltage V_(C1) _(_) ₁ and theresistance value R_(B1) _(_) ₁ _(_) _(k) to the transistor 200 _(A) _(_)_(k) (k=1 to N). When the bias control voltage V_(C1) _(_) ₁ is at a lowlevel and the bias control voltage V_(C1) _(_) ₂ is at a high level, thetransistor 300 _(A) _(_) ₁ is turned OFF and the transistor 300 _(A)_(_) ₂ is turned ON. In this case, the bias circuit 210 _(A3) outputsthe bias current I_(BIAS1) _(_) _(k) determined by the bias controlvoltage V_(C1) _(_) ₂ and the resistance values R_(B1) _(_) ₂ and R_(B1)_(_) ₁ _(_) _(k) to the transistor 200 _(A) _(_) _(k) (k=1 to N). Withthis configuration, it is possible to obtain advantages similar to thoseachieved by the bias circuit 210 _(A1).

FIG. 7 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A4)). Elements equivalent to those of the bias circuit210 _(A1) are designated by like reference numerals, and an explanationthereof will be omitted. The bias circuit 210 _(B) may be configuredsimilarly to the bias circuit 210 _(A).

In the example shown in FIG. 7, the bias circuit 210 _(A4) includes Npairs of transistors 300 _(A) _(_) _(k) and resistors 312 _(A) _(_) _(k)(N>2). In accordance with the N pairs of transistors 300 _(A) _(_) _(k)and resistors 312 _(A) _(_) _(k), N bias control voltages (V_(C1) _(_) ₁through V_(C1) _(_) _(N)) are input from the bias control circuit 240into the bias circuit 210 _(A4).

In the bias circuit 210 _(A4), for example, when the bias controlvoltage V_(C1) _(_) _(k) is at a high level and the other bias controlvoltages are at a low level, among the transistors 300 _(A) _(_) _(n)(n=1 to N), the transistor 300 _(A) _(_) _(k) is turned ON and the othertransistors are turned OFF. In this case, the bias circuit 210 _(A4)outputs the bias current I_(BIAS1) determined by the bias controlvoltage V_(C1) _(_) _(k) and the resistance value R_(B1) _(_) _(k) tothe transistor 200 _(A) (k=1 to N). With this configuration, it ispossible to obtain advantages similar to those achieved by the biascircuit 210 _(A1).

FIG. 8 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A5)). Elements equivalent to those of the bias circuit210 _(A1) are designated by like reference numerals, and an explanationthereof will be omitted. The bias circuit 210 _(B) may be configuredsimilarly to the bias circuit 210 _(A).

The bias circuit 210 _(A5) shown in FIG. 8 includes transistors 800 _(A)_(_) ₁ and 800 _(A) _(_) ₂ (first and second transistors) instead of thetransistors 300 _(A) _(_) ₁ and 300 _(A) _(_) ₂ provided in the biascircuit 210 _(A1). The bias circuit 210 _(A5) also includes a transistor810 _(A) (third transistor) and a resistor 820 _(A) (third resistor). Inaddition to the bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂(first and second bias control voltages), a bias control voltage V_(C1)_(_) ₃ (third bias control voltage) is also input from the bias controlcircuit 240 to the bias circuit 210 _(A5).

The transistors 800 _(A) _(_) ₁ and 800 _(A) _(_) ₂ are field-effecttransistors (FETs). The bias control voltage V_(C1) _(_) ₁ is suppliedto the gate of the transistor 800 _(A) _(_) ₁ via the resistor 310 _(A)_(_) ₁. The bias control voltage V_(C1) _(_) ₂ is supplied to the gateof the transistor 800 _(A) _(_) ₂ via the resistor 310 _(A) _(_) ₂. Thedrains of the transistors 800 _(A) _(_) ₁ and 800 _(A) _(_) ₂ areconnected to the emitter of the transistor 810 _(A). The sources of thetransistors 800 _(A) _(_) ₁ and 800 _(A) _(_) ₂ are connected to theresistors 312 _(A) _(_) ₁ and 312 _(A) _(_) ₂, respectively.

The transistor 810 _(A) is a bipolar transistor, for example, an HBT.The bias control voltage V_(C1) _(_) ₃ is supplied to the base of thetransistor 810 _(A) via the resistor 820 _(A). A power supply voltage ofa predetermined level, for example the battery voltage V_(BAT), issupplied to the collector of the transistor 810 _(A). The emitter of thetransistor 810 _(A) is connected to the drains of the transistors 800_(A) _(_) ₁ and 800 _(A) _(_) ₂. That is, the transistor 810 _(A) isconnected in series with the transistors 800 _(A) _(_) ₁ and 800 _(A)_(_) ₂.

In the bias circuit 210 _(A5), one of the transistors 800 _(A) _(_) ₁and 800 _(A) _(_) ₂ is turned ON under the control of the bias controlvoltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂. Additionally, in the biascircuit 210 _(A5), under the control of the bias control voltage V_(C1)_(_) ₃, the currents to be supplied to the transistors 800 _(A) _(_) ₁and 800 _(A) _(_) ₂ are controlled. For example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 800 _(A) _(_) ₁ isturned ON and the transistor 800 _(A) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(A5) outputs the bias current I_(BIAS1)determined by the bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₃and the resistance value R_(B1) _(_) ₁. When the bias control voltageV_(C1) _(_) ₁ is at a low level and the bias control voltage V_(C1) _(_)₂ is at a high level, the transistor 800 _(A) _(_) ₁ is turned OFF andthe transistor 800 _(A) _(_) ₂ is turned ON. In this case, the biascircuit 210 _(A5) outputs the bias current I_(BIAS1) determined by thebias control voltages V_(C1) _(_) ₂ and V_(C1) _(_) ₃ and the resistancevalue R_(B1) _(_) ₂. With this configuration, it is possible to obtainadvantages similar to those achieved by the bias circuit 210 _(A1).

FIG. 9 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A6)) when the amplifier transistor 200 _(A) is amulti-finger transistor. Elements equivalent to those of the biascircuits 210 _(A2) and 210 _(A5) are designated by like referencenumerals, and an explanation thereof will be omitted. When the amplifiertransistor 200 _(B) is a multi-finger transistor, the bias circuit 210_(B) may be configured similarly to the bias circuit 210 _(A).

The bias circuit 210 _(A6) shown in FIG. 9 includes the same number ofpairs of transistors 800 _(A) _(_) ₁ and 800 _(A) _(_) ₂ (that is,transistors 800 _(A) _(_) ₁ _(_) ₁ through 800 _(A) _(_) ₁ _(_) _(N) andtransistors 800 _(A) _(_) ₂ _(_) ₁ through 800 _(A) _(_) ₂ _(_) _(N),respectively) and the same number of pairs of resistors 312 _(A) _(_) ₁and 312 _(A) _(_) ₂ (that is, resistors 312 _(A) _(_) ₁ _(_) ₁ through312 _(A) _(_) ₁ _(_) _(N) and resistors 312 _(A) _(_) ₂ _(_) ₁ through312 _(A) _(_) ₂ _(_) _(N), respectively), which are provided in the biascircuit 210 _(A5), as the number (N) of fingers.

In the bias circuit 210 _(A6), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 800 _(A) _(_) ₁ _(_)_(k) is turned ON and the transistor 800 _(A) _(_) ₂ _(_) _(k) is turnedOFF (k=1 to N). In this case, the bias circuit 210 _(A6) outputs thebias current I_(BIAS) _(_) _(k) determined by the bias control voltagesV_(C1) _(_) ₁ and V_(C1) _(_) ₃ and the resistance value R_(B1) _(_) ₁_(_) _(k) to the transistor 200 _(A) _(_) _(k) (k=1 to N). When the biascontrol voltage V_(C1) _(_) ₁ is at a low level and the bias controlvoltage V_(C1) _(_) ₂ is at a high level, the transistor 800 _(A) _(_) ₁_(_) _(k) is turned OFF and the transistor 800 _(A) _(_) ₂ _(_) _(k) isturned ON (k=1 to N). In this case, the bias circuit 210 _(A6) outputsthe bias current I_(BIAS1) _(_) _(k) determined by the bias controlvoltages V_(C1) _(_) ₂ and V_(C1) _(_) ₃ and the resistance value R_(B1)_(_) ₂ _(_) _(k) to the transistor 200 _(A) _(_) _(k) (k=1 to N). Withthis configuration, it is possible to obtain advantages similar to thoseachieved by the bias circuit 210 _(A1).

FIG. 10 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A7)) when the amplifier transistor 200 _(A) is amulti-finger transistor. Elements equivalent to those of the biascircuits 210 _(A3) and 210 _(A5) are designated by like referencenumerals, and an explanation thereof will be omitted. When the amplifiertransistor 200 _(B) is a multi-finger transistor, the bias circuit 210_(B) may be configured similarly to the bias circuit 210 _(A).

The bias circuit 210 _(A7) shown in FIG. 10 includes the same number ofresistors 312 _(A) _(_) ₁ (that is, 312 _(A) _(_) ₁ _(_) ₁ through 312_(A) _(_) ₁ _(_) _(N)), which are provided in the bias circuit 210_(A5), as the number (N) of fingers.

In the bias circuit 210 _(A7), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 800 _(A) _(_) ₁ isturned ON and the transistor 800 _(A) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(A7) outputs the bias current I_(BIAS1) _(_)_(k) determined by the bias control voltages V_(C1) _(_) ₁ and V_(C1)_(_) ₃ and the resistance value R_(B1) _(_) ₁ _(_) _(k) to thetransistor 200 _(A) _(_) _(k) (k=1 to N). When the bias control voltageV_(C1) _(_) ₁ is at a low level and the bias control voltage V_(C1) _(_)₂ is at a high level, the transistor 800 _(A) _(_) ₁ is turned OFF andthe transistor 800 _(A) _(_) ₂ is turned ON. In this case, the biascircuit 210 _(A7) outputs the bias current I_(BIAS1) _(_) _(k)determined by the bias control voltages V_(C1) _(_) ₂ and V_(C1) _(_) ₃and the resistance values R_(B1) _(_) ₂ and R_(B1) _(_) ₁ _(_) _(k) tothe transistor 200 _(A) _(_) _(k) (k=1 to N). With this configuration,it is possible to obtain advantages similar to those achieved by thebias circuit 210 _(A1).

FIG. 11 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A8)). Elements equivalent to those of the bias circuit210 _(A5) are designated by like reference numerals, and an explanationthereof will be omitted. The bias circuit 210 _(B) may be configuredsimilarly to the bias circuit 210 _(A).

The bias circuit 210 _(A8) is a modified example of the bias circuit 210_(A5). In the bias circuit 210 _(A8), resistors 312 _(A) _(_) ₁ and 312_(A) _(_) ₂ connected in series with each other are connected to theemitter of the transistor 810 _(A). The drain of the transistor 800 _(A)_(_) ₁ is connected to one end of the resistor 312 _(A) _(_) ₂ and thesource thereof is connected to the other end of the resistor 312 _(A)_(_) ₂. The drain of the transistor 800 _(A) _(_) ₂ is connected to oneend of the resistor 312 _(A) _(_) ₁ and the source thereof is connectedto the other end of the resistor 312 _(A) ₁ .

In the bias circuit 210 _(A8), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 800 _(A) _(_) ₁ isturned ON and the transistor 800 _(A) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(A8) outputs the bias current I_(BIAS1)determined by the bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₃and the resistance value R_(B1) _(_) ₂. When the bias control voltageV_(C1) _(_) ₁ is at a low level and the bias control voltage V_(C1) _(_)₂ is at a high level, the transistor 800 _(A) _(_) ₁ is turned OFF andthe transistor 800 _(A) _(_) ₂ is turned ON. In this case, the biascircuit 210 _(A8) outputs the bias current I_(BIAS1) determined by thebias control voltages V_(C1) _(_) ₂ and V_(C1) _(_) ₃ and the resistancevalue R_(B1) _(_) ₂. With this configuration, it is possible to obtainadvantages similar to those achieved by the bias circuit 210 _(A1).

FIG. 12 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A9)). Elements equivalent to those of the bias circuit210 _(A8) are designated by like reference numerals, and an explanationthereof will be omitted. The bias circuit 210 _(B) may be configuredsimilarly to the bias circuit 210 _(A).

The bias circuit 210 _(A9) is a modified example of the bias circuit 210_(A8). The configuration of the bias circuit 210 _(A9) is the sameconfiguration as the bias circuit 210 _(A8), except that bias circuit210 _(A9) does not include the resistor 310 _(A) _(_) ₂ and thetransistor 800 _(A) _(_) ₂ provided in the bias circuit 210 _(A8).

In the bias circuit 210 _(A9), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level, the transistor 800 _(A) _(_) ₁is turned ON. In this case, the bias circuit 210 _(A9) outputs the biascurrent I_(BIAS1) determined by the bias control voltage V_(C1) _(_) ₁and the resistance value R_(B1) _(_) ₁. When the bias control voltageV_(C1) _(_) ₁ is at a low level, the transistor 800 _(A) _(_) ₁ isturned OFF. In this case, the bias circuit 210 _(A9) outputs the biascurrent I_(BIAS1) determined by the bias control voltage V_(C1) _(_) ₃and the resistance values R_(B1) _(_) ₁ and R_(B1) _(_) ₂. With thisconfiguration, it is possible to obtain advantages similar to thoseachieved by the bias circuit 210 _(A1).

FIG. 13 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A10)) when the amplifier transistor 200 _(A) is amulti-finger transistor. Elements equivalent to those of the biascircuits 210 _(A7) and 210 _(A9) are designated by like referencenumerals, and an explanation thereof will be omitted. When the amplifiertransistor 200 _(B) is a multi-finger transistor, the bias circuit 210_(B) may be configured similarly to the bias circuit 210 _(A).

The bias circuit 210 _(A10) shown in FIG. 13 includes the same number ofresistors 312 _(A) _(_) ₁ (that is, 312 _(A) _(_) ₁ _(_) ₁ through 312_(A) _(_) ₁ _(_) _(N)), the resistor 312 _(A) _(_) ₁ being provided inthe bias circuit 210 _(A9), as the number (N) of fingers.

In the bias circuit 210 _(A10), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level, the transistor 800 _(A) _(_) ₁is turned ON. In this case, the bias circuit 210 _(A10) outputs the biascurrent I_(BIAS1) _(_) _(k) determined by the bias control voltageV_(C1) _(_) ₁ and the resistance value R_(B1) _(_) ₁ _(_) _(k) to thetransistor 200 _(A) _(_) _(k) (k=1 to N). When the bias control voltageV_(C1) _(_) ₁ is at a low level, the transistor 800 _(A) _(_) ₁ isturned OFF. In this case, the bias circuit 210 _(A10) outputs the biascurrent I_(BIAS1) _(_) _(k) determined by the bias control voltageV_(C1) _(_) ₃ and the resistance values R_(B1) _(_) ₂ and R_(B1) _(_) ₁_(_) _(k) to the transistor 200 _(A) _(_) _(k) (k=1 to N). With thisconfiguration, it is possible to obtain advantages similar to thoseachieved by the bias circuit 210 _(A1).

FIG. 14 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A11)). Elements equivalent to those of the bias circuits210 _(A1) and 210 _(A5) are designated by like reference numerals, andan explanation thereof will be omitted. The bias circuit 210 _(B) may beconfigured similarly to the bias circuit 210 _(A).

The bias circuit 210 _(A11) shown in FIG. 14 includes transistors 300_(A) _(_) ₁ and 300 _(A) _(_) ₂ instead of the transistors 800 _(A) _(_)₁ and 800 _(A) _(_) ₂ provided in the bias circuit 210 _(A5).

The collector of the transistor 300 _(A) _(_) ₁ is connected to theemitter of the transistor 810 _(A) via the resistor 312 _(A) _(_) ₁, andthe emitter thereof is connected to the transistor 200 _(A). Thecollector of the transistor 300 _(A) _(_) ₂ is connected to the emitterof the transistor 810 _(A) via the resistor 312 _(A) _(_) ₂, and theemitter thereof is connected to the transistor 200 _(A).

In the bias circuit 210 _(A11), one of the transistors 300 _(A) _(_) ₁and 300 _(A) _(_) ₂ is turned ON under the control of the bias controlvoltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂. Additionally, in the biascircuit 210 _(A11), under the control of the bias control voltage V_(C1)_(_) ₃, the currents to be supplied to the transistors 300 _(A) _(_) ₁and 300 _(A) _(_) ₂ are controlled. For example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 300 _(A) _(_) ₁ isturned ON and the transistor 300 _(A) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(A11) outputs the bias current I_(BIAS1)determined by the bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₃and the resistance value R_(B1) _(_) ₁. When the bias control voltageV_(C1) _(_) ₁ is at a low level and the bias control voltage V_(C1) _(_)₂ is at a high level, the transistor 300 _(A) _(_) ₁ is turned OFF andthe transistor 300 _(A) _(_) ₂ is turned ON. In this case, the biascircuit 210 _(A11) outputs the bias current I_(BIAS1) determined by thebias control voltages V_(C1) _(_) ₂ and V_(C1) _(_) ₃ and the resistancevalue R_(B1) _(_) ₂. With this configuration, it is possible to obtainadvantages similar to those achieved by the bias circuit 210 _(A1).

FIG. 15 illustrates an example of the configuration of the bias circuit210 _(A) (210 _(A12)). Elements equivalent to those of the bias circuit210 _(A8) are designated by like reference numerals, and an explanationthereof will be omitted. The bias circuit 210 _(B) may be configuredsimilarly to the bias circuit 210 _(A).

The bias circuit 210 _(A12) is a modified example of the bias circuit210 _(A8). The bias circuit 210 _(A12) includes transistors 300 _(A)_(_) ₁ and 300 _(A) _(_) ₂ instead of the transistors 800 _(A) _(_) ₁and 800 _(A) _(_) ₂ provided in the bias circuit 210 _(A8). Thecollector of the transistor 300 _(A) _(_) ₁ is connected to one end ofthe resistor 312 _(A) _(_) ₂ and the emitter thereof is connected to theother end of the resistor 312 _(A) _(_) ₂. The collector of thetransistor 300 _(A) _(_) ₂ is connected to one end of the resistor 312_(A) _(_) ₁ and the emitter thereof is connected to the other end of theresistor 312 _(A) _(_) ₁.

In the bias circuit 210 _(A12), for example, when the bias controlvoltage V_(C1) _(_) ₁ is at a high level and the bias control voltageV_(C1) _(_) ₂ is at a low level, the transistor 300 _(A) _(_) ₁ isturned ON and the transistor 300 _(A) _(_) ₂ is turned OFF. In thiscase, the bias circuit 210 _(A12) outputs the bias current I_(BIAS1)determined by the bias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₃and the resistance value R_(B1) _(_) ₁. When the bias control voltageV_(C1) _(_) ₁ is at a low level and the bias control voltage V_(C1) _(_)₂ is at a high level, the transistor 300 _(A) _(_) ₁ is turned OFF andthe transistor 300 _(A) _(_) ₂ is turned ON. In this case, the biascircuit 210 _(A12) outputs the bias current I_(BIAS1) determined by thebias control voltages V_(C1) _(_) ₂ and V_(C1) _(_) ₃ and the resistancevalue R_(B1) _(_) ₂. With this configuration, it is possible to obtainadvantages similar to those achieved by the bias circuit 210 _(A1).

An exemplary embodiment of the disclosure has been discussed above. Inthe power amplifier module 113 including one of the bias circuits 210A₁through 210A₈, 210A₁₁, and 210A₁₂, the ON state and the OFF state of twotransistors are complementarily switched under the control of the biascontrol voltage V_(C1) _(_) ₁ supplied in a first operation mode (forexample, the ET mode) and the bias control voltage V_(C1) _(_) ₂supplied in a second operation mode (for example, the APT mode).Accordingly, the power amplifier module 113 is able to generate a biascurrent determined by the corresponding bias control voltage andresistance value based on the operation mode. It is thus possible tosuitably control bias to be supplied to an amplifier transistor in apower amplifier module that is operable in multiple operation modes.

In the power amplifier module 113 including one of the bias circuits210A₅ through 210A₈, 210A₁₁, and 210A₁₂, the ON state and the OFF stateof two transistors are complementarily switched under the control of thebias control voltages V_(C1) _(_) ₁ and V_(C1) _(_) ₂, and also, thecurrents supplied to these transistors are controlled by using the biascontrol voltage V_(C1) _(_) ₃. Accordingly, the power amplifier module113 is able to generate a bias current determined by the correspondingbias control voltages and resistance value based on the operation mode.It is thus possible to suitably control bias to be supplied to anamplifier transistor in a power amplifier module that is operable inmultiple operation modes.

In the power amplifier module 113 including one of the bias circuits210A₉ and 210A₁₀, the ON state and the OFF state of a transistor areswitched under the control of the bias control voltage V_(C1) _(_) ₁supplied in the first operation mode (for example, the ET mode), andalso, the current supplied to this transistor is controlled by using thebias control voltage V_(C1) _(_) ₃. Accordingly, the power amplifiermodule 113 is able to generate a bias current determined by thecorresponding bias control voltage and resistance value based on theoperation mode. It is thus possible to suitably control bias to besupplied to an amplifier transistor in a power amplifier module that isoperable in multiple operation modes.

The embodiment described above is provided for facilitating theunderstanding of the invention, but is not intended to be exhaustive orto limit the invention to the precise forms disclosed. Modificationsand/or improvements may be made to the invention without departing fromthe scope and spirit of the invention, and equivalents of the inventionare also encompassed in the invention. That is, suitable design changesmade to the embodiment by those skilled in the art are also encompassedin the invention as long as they are within the scope and spirit of theinvention. For example, the elements of the embodiment and thepositions, materials, conditions, configurations, and sizes thereof arenot restricted to those described in the embodiment and may be changedin an appropriate manner. The elements of the embodiment may be combinedas long as such combinations are technically possible, andconfigurations obtained by combining the elements of the embodiment arealso encompassed in the invention as long as they are within the scopeand spirit of the invention.

While embodiments of the invention have been described above, it is tobe understood that variations and modifications will be apparent tothose skilled in the art without departing from the scope and spirit ofthe invention. The scope of the invention, therefore, is to bedetermined solely by the following claims.

What is claimed is:
 1. A power amplifier module comprising: an amplifier transistor to which a first power supply voltage or a second power supply voltage is supplied based on a mode signal supplied to the power amplifier module, the amplifier transistor receiving a first signal and outputting a second signal obtained by amplifying the first signal; and a bias circuit that supplies a bias current to the amplifier transistor, the bias circuit including a first resistor, a first transistor that is connected in series with the first resistor and that is turned ON by a first bias control voltage which is supplied when the mode signal indicates that a first operation mode is to be used to amplify the first signal, a second resistor, and a second transistor that is connected in series with the second resistor and that is turned ON by a second bias control voltage which is supplied when the mode signal indicates that a second operation mode is to be used to amplify the first signal.
 2. The power amplifier module according to claim 1, further comprising: a bias control circuit that outputs the first bias control voltage and the second bias control voltage.
 3. The power amplifier module according to claim 1, wherein the bias circuit further includes a third transistor that is connected in series with the first and second transistors and that is turned ON by a third bias control voltage which is supplied when the first or second operation mode is used.
 4. The power amplifier module according to claim 3, further comprising: a bias control circuit that outputs the first bias control voltage, the second bias control voltage, and the third bias control voltage.
 5. A power amplifier module comprising: an amplifier transistor to which a first power supply voltage or a second power supply voltage is supplied based on a mode signal supplied to the power amplifier module, the amplifier transistor receiving a first signal and outputting a second signal obtained by amplifying the first signal; and a bias circuit that supplies a bias current to the amplifier transistor, the bias circuit including a first resistor, a first transistor that is connected in series with the first resistor and that is turned ON by a first bias control voltage which is supplied when the mode signal indicates that a first operation mode is to be used to amplify the first signal, a second resistor that is connected in series with the first resistor and that is connected in parallel with the first transistor, and a third transistor that is connected in series with the first transistor and that is turned ON by a third bias control voltage which is supplied when the first operation mode or a second operation mode is used to amplify the first signal.
 6. The power amplifier module according to claim 5, further comprising: a bias control circuit that outputs the first bias control voltage and third bias control voltage.
 7. The power amplifier module according to claim 1, wherein the first operation mode is an envelope tracking mode, and the second operation mode is an average power tracking mode.
 8. The power amplifier module according to claim 5, wherein the first operation mode is an envelope tracking mode, and the second operation mode is an average power tracking mode.
 9. The power amplifier module according to claim 1, wherein when the amplifier transistor is a multi-finger transistor having N fingers, the bias circuit includes N pairs of the first transistor and the second transistor.
 10. The power amplifier module according to claim 9, wherein the N pairs of the first transistor and the second transistor are connected in parallel.
 11. The power amplifier module according to claim 1, wherein the power amplifier module is a multi-stage amplifier comprising a plurality of amplifier transistors and a plurality of bias circuits corresponding to the plurality of amplifier transistors.
 12. The power amplifier module according to claim 5, wherein the power amplifier module is a multi-stage amplifier comprising a plurality of amplifier transistors and a plurality of bias circuits corresponding to the plurality of amplifier transistors.
 13. The power amplifier module according to claim 7, wherein the first resistor and the first bias control voltage have values selected in accordance with providing the bias current for the envelope tracking mode and the second resistor and the second bias control voltage have values selected in accordance with providing the bias current for the average power tracking mode.
 14. The power amplifier module according to claim 8, wherein the first resistor and the first bias control voltage have values selected in accordance with providing the bias current for the envelope tracking mode and the first resistor, the second resistor, and the third bias control voltage have values selected in accordance with providing the bias current for the average power tracking mode.
 15. The power amplifier module according to claim 7, wherein the first bias control voltage is greater than the second bias control voltage.
 16. The power amplifier module according to claim 1, wherein when the amplifier transistor is a multi-finger transistor having N fingers, the bias circuit includes one pair of the first transistor and the second transistor.
 17. The power amplifier module according to claim 16, wherein the one pair of the first transistor and the second transistor are connected in parallel.
 18. The power amplifier module according to claim 16, wherein the power amplifier module is a multi-stage amplifier comprising a plurality of amplifier transistors and a plurality of bias circuits corresponding to the plurality of amplifier transistors. 